import pygame

class Ship():

    def __init__(self,ai_settings,screen):
        """初始化飞船并设置其初始位置"""
        self.screen = screen

        # 加载飞船图像并获取其外接矩形

        self.image = pygame.image.load('images/ship.bmp')
        self.rect = self.image.get_rect()
        self.screen_rect = screen.get_rect()

        self.ai_settings = ai_settings

        # 向右移动的flag
        self.moving_right = False
        # 向左移动的flag
        self.moving_left = False


        # 将每艘新飞船放置在屏幕底部中央
        self.rect.centerx = self.screen_rect.centerx
        self.rect.bottom = self.screen_rect.bottom

        # 在飞船的属性center中存储小数值
        self.center = float(self.rect.centerx)

    def update(self):
        if self.moving_right and self.rect.right < self.screen_rect.right:
            # 如果向右移动,且同时x不能超过屏幕的最右边
            self.center += self.ai_settings.ship_speed_factor
        if self.moving_left and self.rect.left>0:
            # 如果向左移动,且同时x不能超过屏幕的最左边
            self.center -= self.ai_settings.ship_speed_factor
        # 根据self.center更新rect对象
        self.rect.centerx = self.center


    def blitme(self):
        """在指定位置绘制飞船"""
        self.screen.blit(self.image,self.rect)